A tangent to a circle at point P is a straight line that touches the circle at P. The tangent is perpendicular to the radius which joins the centre of the circle to the point P. As the tangent is ...

Proctor, on charts for great circle sailing ... in which each point on the sphere is projected on a tangent plane by a line joining the point and the outer end of the tangential diameter; and ...

A tangent to a circle at point P is a straight line that touches the circle at P. The tangent is perpendicular to the radius which joins the centre of the circle to the point P. As the tangent is ...